The present invention relates to elevator systems. More particularly, the invention relates to various embodiments for terminating a flexible flat tension member.
A conventional traction elevator system includes a car, a counterweight, two or more tension members interconnecting the car and counterweights; terminations for each end of the tension members at the connection points with the car and counterweights, a traction sheave to move the tension members and a machine to rotate the traction sheave. A second type of conventional elevator roping system is known to the art as a 2-to-1 roping system where the rope is terminated to a dead hitch and not the counterweight and car. The tension members have traditionally been formed of laid or twisted steel wire which are easily and reliably terminated by means such as a compression terminations and potted terminations.
Compression-type terminations for steel tension members of larger diameters (conventional steel elevator tension members) are extremely effective and reliable. The range of pressures placed on such terminations is reasonably broad without adverse consequence. Providing that the pressure applied is somewhere reasonably above the threshold pressure for retaining the tension members, the termination is effective.
Clamp-type and existing wedge-type and termination devices have been employed for flexible flat tension members and are adept at providing reliable terminations. They are, however, expensive and can be difficult to disassemble, after weighting. The expense related to clamp-type terminations is due to the number of individual components needed as well as the time for installing the same. Existing wedge-type terminations, while being less expensive to manufacture than clamp-type terminations and less time consuming to install, they are still more expensive than is desirable in the industry due to the need for a texturing of the surface to prevent the coefficient of friction on the wedge from dropping below the number required to prevent movement of the tension member therethrough for example if the wedge becomes unintentionally lubricated. Moreover, existing wedge-type terminations when used with flat tension members tend to be difficult to disassemble for maintenance after a load has been placed on them. Thus, the art is still in need of a termination device that reaches an advantageous price point, is easy and timely to assemble and is easy and timely to disassemble.
The above-identified drawbacks of the prior art are overcome or alleviated by the termination device of the invention. The termination device of the invention is a single wedge device wherein the wedge is maintained in position (tension wrapped therearound) by a load side of a socket on one side and on the other side by two pins, one being fixed and one being removable which pins are mounted on said socket. The device operates similarly to other single wedge termination devices in that the wedge is drawn downwardly into a socket to provide compressive force on a tension member threaded between the socket and the wedge. The device of the invention differs, however, in significant ways in that it reliably terminates a tension member while using less material and less height, pinches the flat rope in a desirable location (stronger holding capacity) and additionally facilitates easy assembly and disassembly of the device. While prior art wedge devices are easy to assemble, they are difficult to disassemble as noted above. By employing the removable pin arrangement for the device of the invention, the wedge remains easily removable without regard for creep of the tension member jacket over time. The removable pin is positioned so that when installed it provides excellent support for the wedge and when it is disengaged, allows the wedge to be easily removed from the socket.
In another embodiment of the invention the xe2x80x9cpinchingxe2x80x9d effect on the tension member is provided by a protrusion or bump on the unloaded side of the termination device. The xe2x80x9cbumpxe2x80x9d pinches the tension member providing a stronger holding capacity. Moreover, the location of the bump causes a redistribution of the normal force associated with the load side of the termination device to move compressive force to location experiencing less tensile force.
In another embodiment of the termination devices of the invention a lever concept is employed to terminate a tension member where no additional parts such as wedges are necessary. Rather in the lever embodiment, a tension member need merely be inserted into the device and a load placed on the tension member. The load pulls on one end of the device which imposes a compressive force on the tension member in another end of the device. The concept is applicable primarily to low overhead applications but of course could be used for any application.
In yet still another embodiment of the invention, a rotary termination device is disclosed which provides significant frictional surface area to remove tensile stress in a tension member and simultaneously allows a component of the device having the frictional surface area to rotate and provide a clamping or compressive force to a cut end of the tension member against a second component of the device.